Carbon neutrality-oriented spatial mismatch and flow analysis of carbon stocks and carbon emissions: a case study of Chongqing main city

The balance between carbon stocks (CS) and carbon emissions (CE) is crucial for optimizing regional ecosystem management and enhancing ecosystem carbon sink capacity. Taking the main urban area of Chongqing (MUAC) as the study area, this study integrated the InVEST model, carbon emission coefficient method, CS-CE ratio (CSER), hotspot analysis, and spatial flow field strength model to investigate the spatial mismatch characteristics of CS and CE and their flows patterns from 2000 to 2020. The results showed the following: (1) The average CS declined steadily from 328.63 t to 313.76 t, with high-CS areas coinciding with high-altitude regions. The CE exhibited an inverted U-shaped trend over time, with an overall upward tendency. And high-CE areas were mainly concentrated in the midwestern and northern parts of MUAC. (2) The CSER exhibited a decreasing trend, with the deficit area expanding by 8.3%. Both carbon sink and carbon source areas experienced a fluctuating trend of first increasing and then decreasing. The carbon sink areas remained relatively stable overall, while the carbon source areas expanded by 1.5%. Spatially, the surplus areas were mainly distributed in the northern and southeastern regions, as well as the parallel mountain ranges dominated by Jinyun Mountain, Zhongliang Mountain, Tongluo Mountain, and Mingyue Mountain, whereas deficit areas were primarily located in the central urban areas. (3) The spatial flows magnitudes from CS areas initially increased then decreased, but directional stability persisted. Specifically, Jindaoxia Town in Beibei District remained the core supplier, prioritizing compensation flows to high-CE clusters of Jiugongmiao and Yuejincun in Dadukou District. These research findings can provide critical insights for optimizing carbon resource allocation, achieving carbon neutrality targets, and promoting sustainable urban development.